scholarly journals Membrane fusion during secretion. A hypothesis based on electron microscope observation of Phytophthora Palmivora zoospores during encystment.

1977 ◽  
Vol 73 (1) ◽  
pp. 161-181 ◽  
Author(s):  
P Pinto da Silva ◽  
M L Nogueira
Keyword(s):  
Membrane Fusion ◽  
Freeze Fracture ◽  
Bilayer Membrane ◽  
Phytophthora Palmivora ◽  
Electron Microscope Observation ◽  
Fusion Event ◽  
Vesicle Membrane ◽  
Membrane Bound ◽  
Membrane Contact ◽  
Outer Half

Interpretation of freeze-fracture and thin-section results shows that fusion of the peripheral vesicle with the plasmalemma of a Phytophthora palmivora zoospore occurs at several discrete sites and results in the formation and expansion of a particle-free bilayer membrane diaphragm and in the appearance of a polymorphic network of membrane-bounded tunnels, the lumina of which are continuous with the cytoplasm. The outer half of the bilayer membrane diaphragm appears continuous with the outer half of the plasma membrane; the inner half of the bilayer membrane diaphragm with the inner half of the peripheral vesicle membrane; and the inner half of the plasmalemma with the outer half of the peripheral vesicle membrane. Interpretation of our results leads us to formulate a hypothesis for a sequence of several intermediate stages involved in membrane fusion. The initial fusion event is viewed as a local catastrophe (Thom, R. 1972. Stabilité Structurelle et Morphogenèse. W. A. Benjamin Inc., Reading, Mass.) involving the sudden reorganization of apposed elements of the inner half of the plasmalemma and the outer half of the peripheral vesicle membrane. Fusion of apposed components at the rim of the perimeter of fusion results in the formation of a toroid hemi-micelle which provides continuity between the inner half of the plasmalemma and the outer half of the peripheral vesicle membrane. Simultaneously, apposed components at the site of fusion may reorganize into an inverted membrane micelle. A bilayer membrane diaphragm is then formed by apposition and flowing of components form the outer half of the plasmalemma and the inner (exoplasmic) half of the peripheral vesicle membrane. The existence of large areas of membrane contact before fusion may lead to several fusion events and the formation of a polymorphic network of membrane-bound tunnels.

Studies of membrane fusion. VI. Mechanism of the membrane fusion and cell swelling stages of Sendai virus-mediated cell fusion

1980 ◽  
Vol 43 (1) ◽  
pp. 103-118
Author(s):  
S. Knutton
Keyword(s):  
Membrane Fusion ◽  
Cell Fusion ◽  
Sendai Virus ◽  
Freeze Fracture ◽  
Viral Envelope ◽  
Cell Swelling ◽  
Fusion Event ◽  
Virus Envelope ◽  
Membrane Rupture ◽  
Membrane Tubules

The membrane fusion and cell swelling stages of Sendai virus-mediated cell-cell fusion have been studied by thin-section and freeze-fracture electron microscopy. Sites of membrane fusion have been detected in human erythrocytes arrested at the membrane fusion stage of cell fusion and in virtually all cases a fused viral envelope or envelope components has been identified thus providing further direct evidence that cell-viral envelope-cell bridge formation is the membrane fusion event in Sendai virus-induced cell fusion. Radial expansion of a single virus bridge connecting 2 cells is sufficient to produce a fused cell. Membrane redistribution which occurs during this cell swelling stage of the fusion process is often accompanied by the formation of a system of membrane tubules in the plane of expansion of the virus bridge. The tubules originate from points of fusion between the bridging virus envelope and the erythrocyte membrane and also expand radially as cells swell. Ultimately membrane rupture occurs and the tubules appear to break down as small vesicles. When previously observed in cross-sectioned cells these membrane tubules were interpreted as sites of direct membrane fusion. The present study indicates that this interpretation is incorrect and shows that the tubules are generated subsequent to membrane fusion when 2 cells connected by a virus bridge are induced to swell. A mechanism to explain the formation of this system of membrane tubules is proposed.

scholarly journals Observations of membrane fusion in a liposome dispersion: the missing fusion intermediate?

F1000Research ◽  
2015 ◽  
Vol 4 ◽  
pp. 4 ◽  
Author(s):  
Marianna Foldvari
Keyword(s):  
Membrane Fusion ◽  
Freeze Fracture ◽  
Fusion Event ◽  
Electron Microscopic ◽  
Liposome Dispersion ◽  
Liposome Fusion ◽  
Fracture Electron ◽  
Structural Arrangements

Early intermediate structures of liposome-liposome fusion events were captured by freeze-fracture electron microscopic (EM) technique. The images show the morphology of the fusion interface at several different stages of the fusion event. One of the intermediates was captured at a serendipitous stage of two vesicles’ membranes (both leaflets) merging and their contents starting to intermix clearly showing the fusion interface with a previously unseen fusion rim. From the morphological information a hypothetical sequence of the fusion event and corresponding lipid structural arrangements are described.

Membrane changes associated with mucus production by intestinal goblet cells

1978 ◽  
Vol 33 (1) ◽  
pp. 301-316
Author(s):  
J.G. Swift ◽  
T.M. Mukherjee
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Membrane Fusion ◽  
Thin Section ◽  
Structural Organization ◽  
Freeze Fracture ◽  
Goblet Cells ◽  
Mucus Production ◽  
Membrane Reorganization ◽  
Membrane Changes

Changes in the structural organization of membranes of mucous bodies and the plasma membrane that occur during mucus production in goblet cells of rat rectum have been studied by thin-section and freeze-fracture techniques. Immature mucous bodies are bounded by a trilaminar membrane and fracture faces of the membrane have randomly distributed intramembrane particles. During maturation, mucous bodies become packed tightly together and changes in the structure of their membranes include (1) fusion of apposing membranes of adjacent bodies to form a pentalaminar structure, (2) a reduction in the density of particles on membrane fracture faces, and (3) exclusion of particles from regions of membrane apposition. Some trilaminar membranes of mucous bodies fuse with the lumenal plasma membrane to form a pentalaminar structure. Sites of apposition between mucous body membranes and the lumenal plasma membrane are seen as particle-cleared bulges on fracture faces of the plasma membrane. Our results indicate that membrane reorganization associated with mucous production in goblet cells includes a reduction and redistribution of some membrane proteins and that membrane fusion occurs between portions of membranes from which proteins have been displaced.

scholarly journals The TIP30 Protein Complex, Arachidonic Acid and Coenzyme A Are Required for Vesicle Membrane Fusion

PLoS ONE ◽  
2011 ◽  
Vol 6 (6) ◽  
pp. e21233 ◽  
Author(s):  
Chengliang Zhang ◽  
Aimin Li ◽  
Shenglan Gao ◽  
Xinchun Zhang ◽  
Hua Xiao
Keyword(s):  
Arachidonic Acid ◽  
Membrane Fusion ◽  
Protein Complex ◽  
Coenzyme A ◽  
Vesicle Membrane

Disassembly of the reconstituted synaptic vesicle membrane fusion complex in vitro.

1995 ◽  
Vol 14 (10) ◽  
pp. 2317-2325 ◽  
Author(s):  
T. Hayashi ◽  
S. Yamasaki ◽  
S. Nauenburg ◽  
T. Binz ◽  
H. Niemann
Keyword(s):  
Membrane Fusion ◽  
Synaptic Vesicle ◽  
Vesicle Membrane

scholarly journals Hydrostatic pressures developed by osmotically swelling vesicles bound to planar membranes.

1989 ◽  
Vol 93 (2) ◽  
pp. 211-244 ◽  
Author(s):  
W D Niles ◽  
F S Cohen ◽  
A Finkelstein
Keyword(s):  
Contact Region ◽  
Irreversible Thermodynamics ◽  
Open Channels ◽  
Vesicle Membrane ◽  
Osmotic Swelling ◽  
Solute Permeability ◽  
Membrane Permeabilities ◽  
Membrane Contact ◽  
Planar Membrane ◽  
Planar Membranes

When phospholipid vesicles bound to a planar membrane are osmotically swollen, they develop a hydrostatic pressure (delta P) and fuse with the membrane. We have calculated the steady-state delta P, from the equations of irreversible thermodynamics governing water and solute flows, for two general methods of osmotic swelling. In the first method, vesicles are swollen by adding a solute to the vesicle-containing compartment to make it hyperosmotic. delta P is determined by the vesicle membrane's permeabilities to solute and water. If the vesicle membrane is devoid of open channels, then delta P is zero. When the vesicle membrane contains open channels, then delta P peaks at a channel density unique to the solute permeability properties of both the channel and the membrane. The solute enters the vesicle through the channels but leaks out through the region of vesicle-planar membrane contact. delta P is largest for channels having high permeabilities to the solute and for solutes with low membrane permeabilities in the contact region. The model predicts the following order of solutes producing pressures of decreasing magnitude: KCl greater than urea greater than formamide greater than or equal to ethylene glycol. Differences between osmoticants quantitatively depend on the solute permeability of the channel and the density of channels in the vesicle membrane. The order of effectiveness is the same as that experimentally observed for solutes promoting fusion. Therefore, delta P drives fusion. When channels with small permeabilities are used, coupling between solute and water flows within the channel has a significant effect on delta P. In the second method, an impermeant solute bathing the vesicles is isosmotically replaced by a solute which permeates the channels in the vesicle membrane. delta P resulting from this method is much less sensitive to the permeabilities of the channel and membrane to the solute. delta P approaches the theoretical limit set by the concentration of the impermeant solute.

scholarly journals Phagocytosis of bacteria by polymorphonuclear leukocytes: a freeze-fracture, scanning electron microscope, and thin-section investigation of membrane structure

1978 ◽  
Vol 76 (1) ◽  
pp. 158-174 ◽  
Author(s):  
PL Moore ◽  
HL Bank ◽  
NT Brissie ◽  
SS Spicer
Keyword(s):  
Plasma Membrane ◽  
Electron Microscope ◽  
Membrane Fusion ◽  
Thin Section ◽  
Membrane Structure ◽  
Freeze Fracture ◽  
Vacuole Membrane ◽  
Attachment Sites ◽  
Pmn Leukocytes ◽  
Scanning Electron

The changes in membrane structure of rabbit polymorphonuclear (PMN) leukocytes during bacterial phagocytosis was investigated with scanning electron microscope (SEM), thin-section, and freeze-fracture techniques. SEM observations of bacterial attachment sites showed the involvement of limited areas of PMN membrane surface (0.01-0.25μm(2)). Frequently, these areas of attachment were located on membrane extensions. The membrane extensions were present before, during, and after the engulfment of bacteria, but were diminished in size after bacterial engulfment. In general, the results obtained with SEM and thin-section techniques aided in the interpretation of the three-dimensional freeze-fracture replicas. Freeze-fracture results revealed the PMN leukocytes had two fracture faces as determined by the relative density of intramembranous particles (IMP). Membranous extensions of the plasma membrane, lysosomes, and phagocytic vacuoles contained IMP's with a distribution and density similar to those of the plasma membrane. During phagocytosis, IMPs within the plasma membrane did not undergo a massive aggregation. In fact, structural changes within the membranes were infrequent and localized to regions such as the attachment sites of bacteria, the fusion sites on the plasma membrane, and small scale changes in the phagocytic vacuole membrane during membrane fusion. During the formation of the phagocytic vacuole, the IMPs of the plasma membrane appeared to move in with the lipid bilayer while maintaining a distribution and density of IMPs similar to those of the plasma membranes. Occasionally, IMPs were aligned to linear arrays within phagocytic vacuole membranes. This alignment might be due to an interaction with linearly arranged motile structures on the side of the phagocytic vacuole membranes. IMP-free regions were observed after fusion of lysosomes with the phagocytic vacuoles or plasma membrane. These IMP-free areas probably represent sites where membrane fusion occurred between lysosomal membrane and phagocytic vacuole membrane or plasma membrane. Highly symmetrical patterns of IMPs were not observed during lysosomal membrane fusion.

scholarly journals Endocytosis of synaptic vesicle membrane at the frog neuromuscular junction.

1984 ◽  
Vol 98 (2) ◽  
pp. 685-698 ◽  
Author(s):  
T M Miller ◽  
J E Heuser
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Thin Section ◽  
Nerve Terminal ◽  
Motor Nerve ◽  
Freeze Fracture ◽  
Frog Neuromuscular Junction ◽  
Vesicle Membrane ◽  
Coated Pits ◽  
Active Zones

Frog nerve-muscle preparations were quick-frozen at various times after a single electrical stimulus in the presence of 4-aminopyridine (4-AP), after which motor nerve terminals were visualized by freeze-fracture. Previous studies have shown that such stimulation causes prompt discharge of 3,000-6,000 synaptic vesicles from each nerve terminal and, as a result, adds a large amount of synaptic vesicle membrane to its plasmalemma. In the current experiments, we sought to visualize the endocytic retrieval of this vesicle membrane back into the terminal, during the interval between 1 s and 2 min after stimulation. Two distinct types of endocytosis were observed. The first appeared to be rapid and nonselective. Within the first few seconds after stimulation, relatively large vacuoles (approximately 0.1 micron) pinched off from the plasma membrane, both near to and far away from the active zones. Previous thin-section studies have shown that such vacuoles are not coated with clathrin at any stage during their formation. The second endocytic process was slower and appeared to be selective, because it internalized large intramembrane particles. This process was manifest first by the formation of relatively small (approximately 0.05 micron) indentations in the plasma membrane, which occurred everywhere except at the active zones. These indentations first appeared at 1 s, reached a peak abundance of 5.5/micron2 by 30 s after the stimulus, and disappeared almost completely by 90 s. Previous thin-section studies indicate that these indentations correspond to clathrin-coated pits. Their total abundance is comparable with the number of vesicles that were discharged initially. These endocytic structures could be classified into four intermediate forms, whose relative abundance over time suggests that, at this type of nerve terminal, endocytosis of coated vesicles has the following characteristics: (a) the single endocytotic event is short lived relative to the time scale of two minutes; (b) earlier forms last longer than later forms; and (c) a single event spends a smaller portion of its lifetime in the flat configuration soon after the stimulus than it does later on.

scholarly journals Control of membrane fusion in exocytosis. Physiological studies on a Paramecium mutant blocked in the final step of the trichocyst extrusion process.

1980 ◽  
Vol 85 (2) ◽  
pp. 213-227 ◽  
Author(s):  
J Beisson ◽  
J Cohen ◽  
M Lefort-Tran ◽  
M Pouphile ◽  
M Rossignol
Keyword(s):  
Plasma Membrane ◽  
Membrane Fusion ◽  
Freeze Fracture ◽  
Acid Synthesis ◽  
Extrusion Process ◽  
Membrane Lipid ◽  
Effect Of Temperature ◽  
Physiological Studies ◽  
And Function ◽  
Induced Changes

Previous studies on exocytosis in Paramecium using mutants affecting trichocyst extrusion permitted us to analyze the assembly and function of three intramembrane particle arrays ("ring" and "rosette" in the plasma membrane, "annulus" in the trichocyst membrane) involved in the interaction between these two membranes. Using a conditional mutation, nd9, which blocks rosette assembly and prevents exocytosis at the nonpermissive temperature, we have analyzed the effect of temperature on the secretory capacity of nd9 cells. By combining several techniques (physiological studies, microinjections, inhibition of fatty acid synthesis, and freeze-fracture analysis) we demonstrate (a) that the product of the mutated allele nd9 is not thermolabile but that its activity is dependent upon temperature-induced changes in the membrane lipid composition and (b) that the product of the nd9 locus is a diffusible cytoplasmic component whose interaction with both plasma membrane and trichocyst membrane is required for rosette assembly and exocytosis. The data provide physiological evidence for the existence of a molecular complex(es) linking the two membranes and involved in the control of membrane fusion; we discuss the possible nature and function of these links.

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